Hello, I have a case which I need to retrieve data...

# rx

[Mohamed Ibrahim]

Hello, I have a case which I need to retrieve data from local first then show it, after that retrieve data from API, then override local data, then show the updated version. I started with concat operator and it doesn't work I think because first time there is no local data to get

[kioba]

concat will trigger the second stream only if the first completed

[Mohamed Ibrahim]

Yes I figured that out

[kioba]

try this:

database.publish{
  Observable.concat(it.take(1), Network, it.skip(1))
}

[kioba]

maybe it is share instead of publish but you know the drill

[Mohamed Ibrahim]

Is there any other operator that skip the first stream if it doesn't emit any data

[Mohamed Ibrahim]

I don't think share an publish is a good idea

[kioba]

why?

[ursus]

This honestly is wrong, you should always expose only local data as observable, and then have the api request only write to local -> triggering emit of the local data observable; no need to concat etc

[kioba]

yeah that is the next level, when you just observe the database changes and also trigger an event to request network which updates the database

[kioba]

the reason why we have a concat in our solution is if you have metadata in local database which identifies the last network request. So it will make sure we sync the data when the time comes.

[Mohamed Ibrahim]

I did it with publish and merge and take until, following Kushak example in his Rxjava be examples repo